The invention pertains to a steerable wheel assembly which provides steering control through weight displacement and optionally provides centering and damping forces which moderate the steering behavior.
Many wheeled devices have been invented which benefit or could benefit from the ability to steer by weight displacement. Some of the most widely known are for sport and recreation, such as roller skates. Although very functional and popular, roller skates steer using a bulky mechanism which requires wheels to be in pairs. This limits overall performance in terms of speed, handling, suitable terrain, and makes them heavier than ideal.
Performance gains and wider usage have come from the introduction of in-line skates. These are faster, more maneuverable, and potentially lighter. However, they do not actually steer by weight displacement (although they may at first appear to do so). Steering of in-line skates is accomplished by actually scrubbing the wheels and twisting the skate relative to its direction of motion. This works well only with wheel configurations that have a relatively short wheelbase (shorter than the users foot), or that have central wheels which are lower than the other wheels, creating an effective wheelbase which is short enough to allow turning--a configuration commonly referred to as rocker. For configurations with only two wheels and/or longer wheelbases, steering by scrubbing the wheels is much more difficult. Examples of such devices include land skis, roller skis, and some of the recently introduced all terrain "off-road" in line skates. Typically with these devices steering is accomplished by step turning which is clumsy and difficult. Handling could be greatly improved with weight displacement steering similar to downhill skis.
A wide variety of mechanisms exist for steering individual wheels of sporting devices by weight displacement. However, the known methods have drawbacks which have prevented them from being adopted for in-line skates and land skis as discussed below.
U.S. Pat. No. 4,382,605 (to Hegna, 1983) relies on a chassis comprised of multitude of flexible members which bend and result in steering when the user's weight is shifted. This is complex from a manufacturing standpoint, and potentially unwieldy when used on a foot mounted device such as an inline skate, roller ski, or the like.
The mechanism described in U.S. Pat. No. 3,876,217 (to Copier, 1975) and the similar mechanism used in practice on wheeled land surfing boards both allow the front wheel of a device to pivot about an axis defined by a pivot means necessarily located relatively in front of the front wheel axle. This mechanism is unwieldy because the user's weight is applied to the frame from behind the front wheel, which requires substantially large and potentially heavy supporting members connecting the weight bearing portion of the frame to the pivot means, and additional members to transfer forces between the pivot means and the axle of the front wheel. In both these cases these members form a fork around the front wheel. With the fork, and the additional length of frame required to connect to it, the overall device weight is substantially greater than if the frame could connect directly to the axles of the wheels.
U.S. Pat. No. 4,138,127 (to Kimmell and Stansbury, 1979) describes a mechanism which uses cradle members to provide steering action to wheels of an in-line wheeled device. These cradle members also require a load bearing frame structure which extends to the side of the wheel away from where the user's weight is principally applied in order to create a pivot means with the cradle; for example, for a front wheel, the frame must extend beyond the front of the wheel even though the user's weight is primarily located behind the front wheel. For a device with large wheels, this type of mechanism would require a potentially unwieldy frame structure, similar to those described above.
U.S. Pat. No. 5,372,383 (to Kubierschky, 1994) describes a mechanism which is largely incorporated into the inside of an in-line wheel to provide steering by weight displacement. This mechanism has several disadvantages. As in the case of U.S. Pat. No. 4,138,127, this mechanism requires link members which could be unwieldy for devices with large wheels. Secondly the total amount of steering pivot action obtainable is small because it is limited to the maximum angle obtainable between an axle shaft and an axle tube that surrounds it. For a device with a relatively long wheel base, this would limit the user to large radius turns. Finally, the wheel bearings must be large enough to fit around the axle tube, which would in many cases, prohibit the use of industry standard, inexpensive small skate bearings.
U.S. Pat. Nos. 5,199,727 (to Lai, 1993) and 5,443,277 (to Kubierschky, 1995) describe mechanisms for the same purpose which are both fully contained inside the wheel, and eliminate some of the bulk of the previously mentioned methods. Although they do not require the use of bulky links or cradles, these mechanisms have the following disadvantages:
a) Some if not all of the functional parts of these mechanisms must fit within the inner face of the wheel bearings (as the wheel is viewed from the side). This again necessitates the use of wheel bearings which are larger, heavier and probably more expensive than standard skate bearings. PA1 b) These mechanisms do not lend themselves to the use of standard, inexpensive skate or skateboard wheel bearings for the steering pivot elements because of space constraints. PA1 c) Both mechanisms are limited in total pivot range because of arrangements (similar to U.S. Pat. No. 5,372,383) of a stationary shaft body enclosed by a hollow axle tube body which pivots with the wheel. PA1 d) Finally, the mechanism of U.S. Pat. No. 5,199,727 is subject to having harmful grit and other foreign matter enter into the mechanism unless an elaborate sealing mechanism is added. PA1 a) to provide a mechanism for steering by weight displacement or inclination with respect to the ground which fits within the radius of the wheel and allows the use of standard skate bearings (or virtually any reasonable bearing or bushing) for the primary wheel bearing or bearings as well as for the steering pivot means. PA1 b) to provide a steering mechanism which allows a much larger steering pivot range than is provided for by other mechanisms that can fit inside a wheel of a skate or roller ski. PA1 c) to provide a steering mechanism which can easily be sealed against grit and other foreign material. PA1 d) to provide a steering mechanism which adds the minimum possible weight. PA1 e) to provide a steering mechanism which only requires a supporting frame on one side of the wheel (i.e. with a cantilevered axle) to further reduce the device complexity and structural weight required. PA1 f) to provide a steering mechanism that fits primarily inside the cavity of the wheel of a device so that it is well protected from potentially destructive impact, and to provide a damping and centering force mechanism to moderate steering behavior which fits inside the frame of the device for the same reason. PA1 g) to provide a steering mechanism which can easily be coupled with an adjustable damping and centering force mechanism capable of creating a damped, self centering system to improve handling and maneuverability. PA1 h) to provide a damping and centering force mechanism that can be incorporated into the chassis of a device to be easily coupled with a steering mechanism or other mechanism while adding minimal weight and complexity to the device. PA1 i) to provide a steering mechanism which can be easily disabled by the user so that the rotational axis of the wheel is temporarily fixed with respect to the frame of the device. PA1 j) to provide a sporting device such a skate or roller ski with a simple chassis that is disposed to one side of the foot to provide maximum strength and ground clearance, ease of manufacture, and minimum weight and complexity.
Accordingly, several objects and advantages of the present invention are:
Still further objects and advantages will become apparent from a consideration of the ensuing description and drawings.